Support local development with Docker Compose

[exarkun]

There's already some support for doing local development with minikube. However, minikube requires huge amounts of resources and is not particularly reliable when run for more than a short period. Hopefully minikube will continue to improve and it may be a useful tool for certain bits of local development.

However, Docker Compose is probably an easier thing to use for development that doesn't directly interact with the Kubernetes parts of the system. If we maintain a docker-compose.yml then docker-compose up will be enough to get at least some useful subset of the s4 automation up.